1. Field of the Invention
The present invention relates to a transistor structure, a manufacturing method of a transistor structure and a light emitting apparatus. Specifically, the present invention relates to a transistor structure, a manufacturing method of a transistor structure and a light emitting apparatus regarding a plurality of thin film transistors which control emission of light of light emitting elements which emit light according to a supplied electric current
2. Description of the Related Art
Conventionally, there is known an Electro Luminescent (EL) light emitting display apparatus using an EL element. In the EL light emitting display apparatus, each pixel includes an EL element, and since the EL light emitting display apparatus is driven by an active matrix circuit, a thin film transistor to control the electric current supplied to each EL element is provided in each pixel.
The EL light emitting display apparatus of the active matrix format includes, for example, a switch transistor connected to a signal line (data line) which controls a data signal and a driving transistor which flows electric current to the EL element according to the data signal transmitted from the switch transistor.
It is required that the switch transistor and the driving transistor each have different characteristics so that the EL light emitting display apparatus realizes better light emitting display characteristics.
For example, Japanese Patent Application Laid-Open Publication No. 2007-256926 discloses a technique of a light emitting display apparatus in which a thin film transistor provided with a semiconductor film including crystalline silicon functions as a driving transistor and a thin film transistor provided with a semiconductor film including amorphous silicon functions as a switch transistor.
However, according to the above conventional technique, since either one thin film transistor between the driving transistor and the switch transistor is formed and then the other thin film transistor is formed, film forming of an insulating film, semiconductor film and metallic film and patterning of the formed film is repeated for each thin film transistor in order to form each thin file transistor. Therefore, since each step for each thin film transistor is repeated, about twice as many steps than the normal process is necessary, and there is a problem that the increase in the number of steps results in an increase of manufacturing cost.
Moreover, when light emitted from the EL element, light from outside or the like transmit the insulating film or the bank or reflect on the metallic film and reach the semiconductor film of the thin film transistor, a leak electric current, etc. occurs in the thin film transistor, and with this, for example the characteristic of the thin film transistor composing the switch transistor or the driving transistor may change. Therefore, it is preferable, that such light does not reach the semiconductor film of the thin film transistor.